Electric motor control and differential gear drive for lawn mowers



March 18, 1947.

J. M. RADABAUGH 3 ELECTRIC MOTOR CONTROL AND DIEFERENTIAL GEAR DRIVE FORLAWN MOWER-S Filed Aug. 22, 1944 2 Sheets-Sheet l lam! II I l Inventor 4Joaa JLJZaJaazy/Z 1? I y WW March 18,1947. J. M. RADABAUGH 2,417,613

ELECTRIC MOTOR CONTROL AND DIFFERENTIAL GEAR DRIVE FOR LAWN MOWERS FiledAug. 22, 1944 2 Sheets-Sheet 2 Inventor B; @M'Mim.

WW Em Patented Mar. 18, 1947 FERENTIAL MOWERS GEAR DRIVE FOR LAWN JohnM. Radabaugh, Mount Vernon, Ohio Application August 22, 1944, Serial No.550,591

Claims. (Cl. 18019) This invention relates to. lawn mowers, and theprimary object of the present invention is to provide a mowerof theabove kind including traction'wheels, a rotary knife reel, a reversibleelectric motor, and means operatively connecting the motor with thetraction wheels so that the lawn mower may be selectively propelledforwardly and rearwardly, there being a ratchet driving mechanismbetween the traction wheels and the knife reel so that the latter willbe driven by the motor upon forward travel of the lawn mower but will beallowed to remain idle when the lawn mower is propelled rearwardly.

A further object of the present invention is to provide a lawn mowercharacterized as specified above, wherein the driving connection betweenthe motor and the traction wheels includes a differential gearing thatallows the traction wheels to travel at different speeds so as tofacilitate negotiation of turns in using the mower.

A still further object of the present invention is to provide a lawnmower of the above character having a handle employed solely forsteering the lawn mower, as defined from causing travel thereof, saidhandle having handle bars or grips respectively operable for controllingthe direction of travel of the lawn mower by controlling the directionof rotation of the drive shaft of the motor and for controlling thespeed of operation of the motor.

Still another object of the present invention is to provide a lawn mowerof the above character embodying a frame having means for mountingstorage batteries thereon rearwardly of the knife reel and the lower endof the handle, said batteries providing current for operation of thedriving motor, the frame also supporting a battery charger and anoverload relay or circuit breaker so that the batteries may beconvenientlyrecharged from time to time as found necessary, and so thatthe motor will be auto matically thrown out of operation when overloadeddue to clogging of the knife reel orthe mower constructed in accordancewith the present invention.

Figure 2 is an enlarged fragmentary vertical section taken substantiallyupon the plane of line 2-2 of Figure l.

Figure 3 is a fragmentary horizontal section taken substantially uponthe plane of line of Figure 2, with parts omitted.

Figure 4 is a fragmentary vertical section taken on line 4-4 of Figure1.

Figure 5 is a wiring diagram showing the electrical system embodied inthe mower of Figure 1,

Referring in detail to the drawings, the present mower includes asuitable frame 5 embodying spaced rigidly connected side plates or discs6 at the outer sides of which are journaled coaxial traction wheels 1.discs 6 at the lower portions of the latter is a transverse bar 8 onwhich is fixed the stationary knife or bladeQ of thelawn mower thatcooperates with the knives l0 of a rotary cutting reel in a manner wellknown in the art. This cutting reel has a driven shaft ll whose ends arejournaled in the discs 6 forwardly of and above the fixed knife 9 andproject within the traction wheels 7 where they are provided withpinions l2 meshing with the teeth of internal ring gears 13 carried bythe traction wheels 1. A ratchet driving connection is. provided at I4,in a well known manner, between the ends of the shaft II and the pinions12, so that when the lawn mower travels forwardly, drive is transmittedfrom the traction wheels 1 to the cutting reel, but, upon rearwardmovement of the lawn mower, the cutting reel is allowedto remainstationary or to idle.

Adjacent one side, the frame 5 is provided with a bracket l5 to which issecured anelectric motor I6 disposed with its power or armature shaftvertical and projecting upwardly. The projecting end of the power orarmature shaft I6 of motor I6 is provided with a worm l1 mesh ingwiththeworm ring gear [8 of a differential gearing generally; indicated at[9. The differand meshing with said beveled gears I90. A' transverseaxle housing 20 connects the discs 6 a and has coaxial shafts 2i and 22journaled there- Rigidly connecting the in and operatively connected attheir adjacent inner ends by means of the differential gearing Ill. Thehousing 20 is formed near one end with a casing 23 for the differentialgearing l9 and worm l1, and the shafts 2| and 22 respectively projectwithin the traction wheels 1 and have pinions 24 secured on the outerends thereof and meshing with the ring gears l3 of said traction wheelsi. It will thus be seen that the reversible motor [3 may be driven ineither direction so as to drive the traction wheels for causing eitherforward or rearward travel of the lawn mower. Also, the differentialgearing l9 permits each traction wheel I, to rotate faster than theother for facilitating negotiation of turns during forward and rearwardtravel of the lawn mower.

Fixed at its ends to the discs 6 is a yoke 25 having an elongated handle26 rigid with and projecting upwardly and rearwardly from the centralportion thereof. The handle 23 is utilized for steering the lawn mowerduring travel thereof, and it is provided at its upper rear end withhandle bars or hand grips 21 and 21a that project laterally in oppositedirections and are axially rotatable relative to the handle 26, theiraxes of rotation being indicated by dotted lines at 28 in Figure 1.

The frame is provided at a point between the discs 6 and directly behindthe yoke 25 with a shelf support 29 for a plurality of electric storagebatteries 30 that are electrically connected in series with each other.The frame is also providedben'eath the support 29 with another shelfsupport 3| for a portable electric battery charger 32 and an overloadcircuit breaker or relay 33. The battery charger 32 has a suitableattachment cord equipped at its free end with an ordinary attachmentplug 34, as indicated in Figure 5, so that current may be derived froman ordinary house Wiring system to utilize the battery charger forcharging the batteries 30. As shown, the battery charger includes atransformer 35 adapted to step down the voltage and change the currentfrom alternating to direct so that current of the proper kind andvoltage is supplied to the batteries 30 when the latter are beingcharged. The charger also includes a non-return condenser 33 by means ofwhich the current is allowed to flow from the transformer 35 to thebattery but is prevented from returning from the battery or flowing inthe reverse direction. This action is due to the different metals usedfor the respective sets of plates of the condenser.

The relay or circuit breaker 33 includes a coil 3'! and a core 38forming a solenoid in which the core 38' is moved upwardly whenattracted. The core 38 is arranged to actuate a pivoted contact 39normally engaged with a stationary contact 40. Thus, the contacts 39 and40 are normally engaged to close a circuit, and when the circuit isoverloaded, the core 38 moves upwardly and swings "the contact 39 out ofengagement with contact 40 so as to break the circuit. As shown inFigure 5, the circuit of motor I6 is controlled by a reversing switch 4|mounted in the upper end of handle 26 and operable by the hand grip orbar 21. Also, the supply of current from the batteries 30 to the switch4| may be regulated by means of a rheostat or manually adjustableresistance 42 that is also mounted in the upper end of handle 26 andoperable by the hand grip or bar 21a. One side of the solenoid coil 31is connected'at 4-3 with one sideof batteries 30, while the other sideof batteries 30 is connected at 44- 4 to the resistance of rheostat 42.The movable contact of rheostat 42 is connected at 45 with one blade ofreversing switch 4|, the other blade of switch 4| being connected at 46with the contact 39 of relay or circuit breaker 33. Contact 40 ofcircuit breaker or relay 33 is connected to the other side of solenoidcoil 3?, and the reversing switch 4| has four fixed contacts a, b, c and(Z. Contact a is connected at 47 with contact d and contact b isconnected at 48 with contact 0. The blades of switch 4| maysimultaneously engage contacts a and b or c and d, and it will thus beseen. that the position of the blades of the switch 4| will govern thedirection of rotation of the armature of motor It. In either position ofthe switch 4|, the contacts 39 and 40 will be included with the solenoidcoil 31 in series with the blades of switch 4|. Thus, the switch 4| maybe thrown from inoperative position to either operative position byturning the hand grip 2'l in the proper direction, and the speed ofoperation of motor l3 may be controlled by turning hand grip 21a in theproper direction. When hand grip 27 is turned in one direction, motor I6is driven so as to cause forward travel of the lawn mower and to drivethe cutting reel. When hand grip 27 is turned in the opposite direction,the motor i6 is reversed so as to cause rearward travel of the lawnmower without driving the cutting reel. The speed of travel in eitherdirection is governed by actuation of rheostat 42 by turning hand grip21a. Should the motor circuit become overloaded for any reason, such asclogging of the cutting reel, the relay 33 will be actuated to open themotor circuit and prevent damage to the motor or the parts of the lawnmower actuated thereby. It will be noted that a space is provided besidethe relay 33, as at 49, for convenient storing of the attachment cord ofthe battery charger 32 when the latter is not in use. It will also beunderstood that any'suitable means may be provided for detachablyconnecting the battery charger to the batteries only while the latterare being charged. An obvious advantage of this arrangement is that thelawn mower carries its own source of electricity and the means forreplenishing the current of such source from time to time as foundnecessary, thereby rendering it unnecessary to always have a trailingattachment cord running from the lawn mower to the outlet receptacle ofa house wiring system.

From the foregoing description, it is believed that the construction andoperation, as well as the advantages of the present invention, will be.readily understood and appreciated by those skilled in the art. It willbe apparent that the device is comparatively simple in'construction,durable, efficient and convenient to use.

While I have illustrated and described a preferred embodiment of theinvention, it will be understood that the invention is susceptible tomodification and minor changes in details of construction withoutdeparting from the spirit and scope of the invention as claimed.

It will be noted that the charger is an active element in the operationof the motor and lawn mower due to the relay associated therewith.Specifically, the charger is interposed between the batteries and themotor so as to coact therewith.

What I claim is:

1. In a hand guidedlawn mower having a rotary cutting reel, thecombination of a frame having a handle,,co-axial traction wheelsjournaled at opposite sides of the frame and having 2,417,618 internalring gears, aligned axles journaled trio motor vertically mounted on theframe and transversely of the frame and having pinions having anupwardly projecting armature shaft, a fixed on their outer ends in meshwith said ring driving connection between the armature shaft of gears, adiiierential gearing between the inner said motor and the ring gear ofsaid differential ends of said axles including a spider-carried ring 5gearing, a manually operable reversing switch gear, a reversible rotaryelectric motor vertically for said motor, a handle fixed to the framefor mounted on the frame and having an upwardly steering the mower, handgrips carried by and projecting armature shaft, a driving connectionprojecting from opposite sides of said handle, one between the armatureshaft of said motor and of said hand grips being axially rotatableandopthe ring gear of said differential gearing, and a eratively connectedto said reversing switch, and, manually operable reversingswitch forsaid moa rheostat for controlling the speed of said motor carried by thehande. tor, the other hand grip also being axially rotat- 2. In a handguided lawn mower having a roable and operatively connected to saidrheostat. tary cutting reel, the combination of a frame, 4. Theconstruction'defined in claim 1, i co co-axial traction wheels journaledat opposite bination with a rearwardly facing shelf on the sides of theframe and having internal rin frame rearwardly of said axles and abovethe mogears, aligned axles iournaled transversely of tor, electricstorage batteries supported on said the frame and having pinions fixedon their outs e and l t y connected t the mot r er endsin mesh with saidring gears, a differenthroug said reversing switch. tial gearing betweenthe inner ends of said axles 2 5. The construction defined in claim 1,in @0111- including a spider-carried ring gear, a reversible binallimlth a wa y g" supelimposed rotary l ctri m to v rtic ll t d on th shelveson the frame, electric storage batteries frame and having an upwardlyprojectingarmasupported on the upp s one f sa d s l s, ture shaft, adriving connection between the ara ,charg'fir f r S batteries Supportedy the mature sh ft of said mot nd th in gear of other shelf beneath thebatteries, said storage said differential gearing, a manually operablerebatteries being electrically connected to the moversing switch forsaid motor, a handle fixed to o through said reversin t the frame forsteering the mower, and hand grips OHN M- RADABAUGH. carried by andprojecting from opposite sides of '1 said handle, one of said hand gripsbeing axially 3 7 REFERENCES CITED rotatableand operatively connected tosaid re- The following references are of record in th versins switchfileof this patent: V

3. In a hand guided lawn mower having a retary cutting reel, thecombination of a frame, UNITED STATES PATENTS coaxial traction wheelsjournaled at opposite Number Name Date sides of the frame and havinginternal rin'ggears, 1 753,284 Maxim Mar. 1, 1904 alignedaxles'jou'rnaled transversely of the frame 1,115,350 Vincent Oct. 27,1914 and having. pinions fixed on their outer ends in 2,185,659 ChernowJan. 2, 1940 mesh with said ring gears, a difi'erential gearing2,298,135 Klein Oct. 6, 1942 between the-inner ends of said axlesincluding a 0 2,300,461 ODellet a1 Nov. 3, 1942 spider-carried ringgear, a reversible rotary eleci

